Necrotizing enterocolitis (NEC) is a major concern in the neonatal intensive care unit, causing great morbidity and mortality. My long-term career goal is to elucidate the molecular mechanisms that lead to the development of NEC in the premature newborn infant. This will lead to the prevention and treatment of this devastating disease. My short-term goals are to gain knowledge and novel technical skills (such as in vivo gene transfer and laser-capture microdissection) that will enable me to make significant contributions in the field of NEC research and to become an independent research scientist. This award would allow the necessary support to achieve these goals, under the mentorship of Dr. Michael Caplan and Dr. Terrence Barrett in an excellent research environment. We have preliminary evidence that the transcription factor nuclear factor- (NF-kB) is developmentally regulated in the intestine and is persistently activated in a neonatal rat model of NEC. My overall hypothesis is that NEC results from the prolonged activation of NF- kB in the premature intestine in response to bacterial products and locally produced inflammatory lipid mediators such as platelet-activating factor (PAF), causing neutrophil infiltration and necrosis. In the premature infant, this persistent NF-kB activation leads to the upregulation of pro-inflammatory cytokines (e.g. TNF), chemokines (e.g. MIP-2) and adhesion molecules (e.g. ICAM-1) which amplify the inflammatory response. As a result, neutrophils are mobilized and activated, causing irreversible tissue injury and necrosis. The following specific aims will be addressed: 1) to characterize NF-kB activation in the neonatal model of NEC induced by hypoxia-cold stress-formula feeding; 2) to study the role of NF-kB in the neonatal NEC model and its mechanisms of action in a model of acute bowel injury; 3) to examine the effect of modulating the intestinal flora and treatment with probiotics on intestinal NF-KB activation in the neonatal NEC model. To do so, several transgenic mice models are proposed: mice lacking or over-expressing a specific subunit of NF-kB, reporter mice expressing NF-kB-dependent luciferase and finally in vivo gene transfer will be used. Understanding the developmental differences in the NF-kB activating pathway might lead to specific strategies geared at inhibiting NF-kB activation in the early stages of necrotizingenterocolitis. This could prevent its progression toward irreversible intestinal damage and improve the survival of premature infants. [unreadable] [unreadable]